It's possible. Where is the etched number? The AKM receiver started in 1972 and the Yugoslavian military used only the folding stock version. Maybe the fixed stock RPK receiver M70 started at the same time. Maybe the Zastava history is referring to the M72 getting a stamped receiver in 1974. I'll try to read it again but I remember seeing no reference to the M72 and only the M70 or the AK. Zastava history says the threaded barrel models were called M67's until the Yugoslavian military adopted them in 1970 as the M70. Those don't have a model number marked on them.

The electro numbers are on all the parts as well as the standard engraved serial numbers. Both numbers match on all parts. There is no year or anything else stamped on the front trunnion.

I have photographed every year from 1982-1990, and few unmarked. 1982 is the earliest "dated" rifle I have found. My old "slabside" kit was dated 1982 as well.

The M72s follow a similar pattern... Earlier models had sterile trunnion and serial number on right side (like milled guns).

82 ended spot welding trunnion to receiver.

Engraved RSB changed about 85/86.

By slabside, you mean the 0.9 mm AKM style receiver? That would show they were made during the same years as the RPK style receiver M70.

The M80, M82 RPK and M85 started production in 1985. The M80 and the first M85 had the AKM style receiver and spot welded trunnions. The first M85 had a shorter barrel that was AKS-74u length. In 1990 the RPK receiver M90, M90 RPK and M85M went into production. From what I've seen, these did not have spot welded trunnions. The M85M had the newer, longer barrel. Zastava shut down production in 1992 due to sanctions. When production resumed, the M85M was renamed to M85.

I haven't paid much atention to years the M70's have spot welded trunnions but all of the mid-1980's slabside 5.56 M80's I've seen have spot welded trunnions. I saw a 5.56 RPK without spot welded trunnions. I think it was an M82 but it may have been an early M90 RPK considering the year I saw it.